He looks at her as if she's just grown horns "Glass?"
She can't help grinning at the look on his face, a mix of disappointment and incredulity. "You ever wondered why staring in through a shop window, face pressed up against the glass, doesn't set any alarms off? Or looking through the window of a neighbour's house?"
"Nooo" he says slowly, bending his mind to the question, a puzzled frown taking over as he thinks it through. "Ok, I'll bite, why?"
"We said humans have a skin temperature of about ninety-three degrees Farenheit right?" He nods, "In infrared wavelengths, that's about nine or ten micrometers, so sensors are typically set to detect between ranges of eight to twelve microns …" here she pauses for effect and grins at his impatient movements in the chair, "… glass blocks wavelengths longer than about two point seven microns, which basically means you are invisible to PIRs if you're behind glass"
Again she pauses for a sip of coffee and watches him digest the information, rather enjoying this tutelage.
"So, what? You mean you have to carry a big sheet of glass round with you?"
"Well, yes, or at least that's how you'd have had to do it until recently …" unable to hide her smile of anticipation, oh he's so going to love this! "However, there's another problem, with the glass sheet or whatever …" she looks around, "… see that drinks dispenser over there?" she asks, and when he nods, continues "… there's a pump keeping the drinks cool in there, a bit like a fridge, the motor for that pump will get pretty hot after a few hours running. PIR sensors not only go off when human wavelengths of infrared appear or disappear within detection zones, but also if an object suddenly blocks a strong infrared pattern in the background, so if a background infrared pattern disappears and then reappears in the same zone, it satisfies one of the criteria for alarm"
He nods in understanding "So how do you solve that?"
"By scouting out the premises beforehand, find out where machinery is placed … things like computers aren't likely to be on if you're calling after hours, but food or drinks dispensers, radiators or heat pumps, strong lights, anything with a micron value of three or more, you need to know where they are in reference to the PIRs, if they're within a thirty foot radius then you need to turn them off without getting between them and the PIR or you need to cut power to the floor or the building … but that's just as likely to set alarms off anyway"
"Wouldn't tuning the power off be just as bad as blocking?"
"Nope, the heat from the machinery or lights would dissipate slowly, in the same way as they would warm up slowly once they're turned back on. That won't set off any alarms, imagine what would happen when there's a power cut, you'd have alarms going off all over the city … it's the sudden change that does it"
"Ok, I got it … but you said the glass sheet was how you would have had to do it?" and she can't help laughing at the fact that that had stuck in his mind. She nods.
"Yeah, you know those shields riot police use?" he nods, "You'd have had to get some glass cut to about those measurements and it would have to be laminated or tempered to avoid smashing it if you walked into something, you'd also have to fix some grips to the inside so you could hold it from behind … which would raise some eyebrows in the glass-cutters …" and again she gives him a smile, "… or you go to a scrap yard, get a rear window, something like a Ford Station Wagon's, pick up a couple of rubberised handles and some superglue from your local DIY, and hey presto, one anti-PIR shield"
He's shaking his head and looking at her in admiration "Wow!"
"Yeah, but here's the good thing, you can now get spray-on liquid glass!" and much as she'd anticipated, he's loving it. "It's flexible, consists of almost pure silicon dioxide, and the glass coating bonds to just about any surface. So all you need to do is get a full wet suit, spray it with SiO2 making sure you cover every bit … and hey presto, all you have to do is avoid blocking heat sources!"
"Where can you get the stuff?" he asks in excitement, and she can already see him trying to get some to play with.
"Not that easy over here yet, it was invented in Turkey and the patent's held by a German company called Nanopool. Trials are being run in Germany and the UK, and over there it's already being used to coat all sorts of things … you can pick it up in DIY stores for about eight bucks … I had a friend send me a box … and no, you can't have any!" to which he pouts and gives her his kicked puppy look, she just shakes her head "uh-huh, not going to work Castle!"
He resigns himself to it for the moment, deciding he can probably get a box sent to him without any problem, and turns to his original question, "Ok, so you've told me what to look out for, how would you get in here?"
"Just give me a minute will you, need to go visit the ladies'" and she pushes back from the table before heading off to the rest rooms. When she returns she sits down, looks at the empty cup but decides she's had enough and pushes it to one side before resuming the conversation.
"First problem's the lobby guards, you either have to get hold of a pass to get you through the turnstiles and hope none of them spots you as a stranger, or you have to get an invite like you did, which means you leave a trail that can easily be followed, or you have to get through without any of them noticing you"
"How d'you do that?"
"Easy way? Take a look at their magazines, see what they're offering in the way of jobs or work opportunities and get an interview, try and make it an advertising or IT one, a job that will allow you to bring a case or bag in … they'll go through it at security, but the stuff in there should look pretty innocent. That will get you into the building and up onto whichever floor it is … when you're waiting or about to sit for the interview, get an urgent call that has you having to leave, all full of apologies and ass-kissing, get into a lift and head up a floor or two. Without knowing what I'd find there I can't be very precise but I'd head for a restroom … most of them have acoustic tiles to bring the ceiling down to a reasonable height and to hide all the piping and air ducts and cables running overhead. I'd just shift one of the tiles near the back wall of the cubicle when no one's around, climb up there and find somewhere to hang some slings from … there'll always be some heavy duty anchor points amongst all the industrial stuff up there. Put the tile back in place and settle yourself into the slings. Then it's just a waiting game, allowing the building to go to sleep before dropping down and heading off to whatever you want to do. That's really why you need floor plans and eyes-on beforehand, so you're not blundering around the place, especially at night"
"And the difficult way?"
"Come in as late as possible and when most of the workforce is about to leave or just leaving. Cause a distraction, pay someone to have a heart attack or a panic attack or scream blue murder because they've been pickpocketed, you'll probably only have a few seconds before one of the guards turns back to check the area, but by then you should be through and up the escalators. Once you're up here you've got breathing space, but you can't hang around too long. I've just had a quick look, the lifts are round behind that wall in two banks and there are security cams and PIRs there but that in itself wouldn't be a problem, you'd just get on one of them and head up to into the tower, then the restroom number"
He's nodding but was obviously hoping for something more dramatic. She looks at him in amusement and waits him out. Eventually he looks at her, "Ok, thanks for that, how about we head home, get changed and go out somewhere for a bit of lunch?"
"My clothes not smart enough now?" she asks, partly mocking, partly surprised.
"Too smart for where we're going" he says, standing up and taking her hand. They make their way down the escalators and out into the street, looking back and up at the tower rising above them "How about climbing up there?" he asks, only half joking.
"The structure's easy to climb but you'd have to smash your way in through the glass or make it all the way to the top and find a route in from there … and there are probably more security measures up there than anywhere else … you'd only need to land a chopper otherwise"
With a final look they turn and start looking for a cab.